An IPTV multicast channel change delay is an important factor of a Quality of Experience (QoE) indicator of an IPTV service. The channel change delay is a time from a point at which a user operates a remote control to initiate a channel change request to a point at which an image of a requested channel appears on a television screen.
A channel change of IPTV is different from that of conventional television and digital television. In a conventional cable television network, a terminal receives all channel signals at the same time, and a channel change time is approximately 0.5 second. Because of a decoding process, a channel change time of the digital television is slightly longer than that of cable television, but is generally below 1 second. The IPTV is limited by bandwidth of an access network, and a terminal can receive only one channel signal at a time. In addition, a channel change process of the IPTV requires complex network signaling interworking. As a result, an accumulated IPTV multicast channel change delay may be relatively long.
A fast channel change (FCC) is a method for reducing a channel change time by delivering, by an FCC server, a special unicast program stream beginning with an I-frame. By means of FCC service deployment in a network, an I-frame waiting time and a network signaling interworking time can be avoided, and an I-frame transmission speed can be increased, thereby increasing a channel change speed.
However, during channel change processing, playback of a channel image depends on whether the terminal can receive both a video packet and a corresponding audio packet, but an interval between an audio packet and a video packet in a channel live stream in an existing network cannot be controlled, which restricts delay control of an FCC fast channel change. Therefore, a delay of normal playback (a moving image fully synchronized with a sound) of a target channel after the channel change is increased, and user experience is affected.